With environmental standards continually changing and requiring stricter emission controls and tighter air quality standards, there is a continual need for new and improved devices to help reduce exhaust gas emissions from internal combustion engines and the like. More specifically, devices that require fewer components, that are less costly to manufacture, and that are easier to maintain are desirable.
When considering diesel engines, for example, these engines are known to discharge exhaust gases that contain several constituents that are harmful to human health and to the environment. In order to reduce harmful exhaust emissions, diesel traps or filters and diesel catalysts are often used. Diesel particulate filters (DPF) control diesel particulate matter emissions by physically trapping the particulates within the device. Diesel catalysts control emissions by promoting chemical changes in the exhaust gas and are most effective towards reducing gaseous emissions, i.e., hydrocarbons and carbon monoxide. Diesel particulate filters and diesel catalysts may be used independently or in combination with each other or with other after-treatment devices.
While diesel particulate filters can achieve very high soot (i.e. particulate matter) removal efficiencies, they are limited in the sense that they eventually become blocked with the particulate matter. Therefore, it is desirable to find ways to regenerate the filter from the particulate matter in a reliable, cost-effective manner. Diesel oxidation catalysts, which are used to increase the temperature upstream of the DPF, operate most efficiently at higher temperatures; therefore, it is desirable to find ways to heat catalysts so as to bring them to their optimal operating temperature to ensure reduction of exhaust gas emissions, especially particulate matter in the case of diesel engines. Various techniques have been adopted to assist with and/or improve the regeneration of the particulate matter from filter devices as well as to improve the efficiency of catalytic devices, such as the installation of a burner, or an after-treatment device to burn particulate matter and unburnt hydrocarbons, and/or heat up catalytic components which are useful to increase the temperature of exhaust gases and reduce emissions. These burners, however, often require the installation of complex components that rely on external or auxiliary air compressors (or blowers) as well as high pressure fuel injectors and they tend to be costly to produce, difficult to maintain, and difficult to tailor to a particular application to ensure that optimal results are achieved in reducing exhaust emissions for a particular application.
Therefore, with environmental concerns continually on the rise, it is desirable to provide simplified, easily tailored, burners or exhaust gas after-treatment devices which can assist in reducing harmful exhaust gas emissions and improve local air quality.